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An Investigation into the effect of varying enzyme concentration on the rate of an enzyme controlled reaction.

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Planning An Investigation into the effect of varying enzyme concentration on the rate of an enzyme controlled reaction The aim of my experiment is to see whether there is a relationship between the enzyme concentration and the initial rate of the reaction. The reaction involves catalase breaking down hydrogen peroxide, which is the substrate. The enzyme is yeast. This is the reaction: 2H2O2(l) --> 2H20(l) + O2(g) Background Knowledge Enzymes are biological catalysts, which are made up from groups of protein molecule. An enzyme has an active site, which has a unique shape (lock) into which only a substrate of the exact same unique shape (key) can fit. When this substrate links into the active site it forms something called an enzyme-substrate complex. Catalysts are substances, which speed up the rate of a reaction, but do not get used up themselves. Enzymes will denature in certain conditions. These conditions are high temperatures and high levels of pH. The bonds that hold enzymes together are weak and so are easily broken by these factors. If these bonds are broken the enzyme, along with the active site, gets deformed. This is called a denatured enzyme. There are two types of enzymes, Extracellular Enzymes and Intracellular Enzymes. Extracellular enzymes are enzymes that can control reactions, which happen outside cells. ...read more.


increase; the rate of reaction will also increase. This is because the time taken for the hydrogen peroxide to break down will decrease, thus increasing the rate of reaction. I also predict that the rate of reaction and concentration of enzyme will be directly proportional to the amount of enzyme, until they get to a point were the enzyme will have denatured.. I based my hypothesis on the lock and key theory and the collision theory. As the higher the enzyme concentration is the more collision will occur and the faster the rate of reaction will be. Pilot Study Firstly I did a pilot study, by recording data for 2% and 10% enzyme concentration. I needed to dilute the enzyme to only two concentrations using the dilution table. I used this table also for the actual experiment. The data I obtained from this investigation has been recorded in a table showing the time, enzyme concentration and rate of reaction. Time Volume of oxygen collected for concentration for concentration 2% Volume of oxygen collected for concentration of 10% yeast. 0 0 0 0 0 5 4 3 20 22 10 6 5 32 26 15 9 8 38 30 20 11 9 41 40 25 13 12 42 41 30 15 13 43 43 35 17 16 43.5 43.5 40 20 19 44 43.5 45 21 21 44 44 50 23 23 44 44 55 25 25 ...read more.


Its shows how the collision theory is correct, as the more enzyme concentration there is the faster the reaction is. This is because as the enzyme concentration goes up, there are more molecules that collide with each other and so the rate of reaction is faster. There didn't seem to be any obvious anomalous results, as most of the results seemed wrong. This could be due to the fact the tests were done on 3 separate days and on all these day there was different temperatures. There was also the problem of reaction time, as it took time to get the bung on once the yeast was put in, as well as the time it took from when it was put in to when the stopwatch was started. There were also delayed reactions between when you shout NOW to when the other person says the amount and when you write it down. These problems could have been sorted out by using a data logger, this would have also produced graphs, which would have been more accurate than hand drawn ones. I think that if I did this experiment again I would do more than 3 tests for each concentration to ensure I got better results. I would also try and do all my tests on the same day, so there was the same temperature. I would also use a buffer, this would ensure that the pH was kept at 7 for the whole experiment. ...read more.

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